Process for Producing a Hyper-Elastic, High Strength Dilatation Balloon made from Multi-Block Copolymers

ABSTRACT

A self-wrapping dilatation balloon comprising a multiblock copolymer having high elasticity and elastic recovery from nominal strains greater than about 30% is described. Also described herein, is a polymeric extrudate for making a dilatation balloon comprising a multiblock copolymer having tensile strength in the range of about 50 MPa to about 450 MPa, strain at break in the range of about 50% to about 600% and substantially complete elastic recovery from nominal strains of at least about 30%. The extrudate has phase-separated microdomains that are macroscopically aligned in parallel, perpendicular, transverse or a combination thereof. Also described herein is a process for producing a polymeric extrudate for use as a dilatation balloon. The process comprises extruding a multiblock copolymer mixture or composition to form an extrudate. The extruding is done such that the extrudate has phase-separated microdomains that are macroscopically aligned in parallel, perpendicular, transverse or a combination thereof. After extrusion, the process optionally comprises the steps of drawing and coagulating the extrudate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 10/920,458, filed Aug. 18, 2004, which claims thebenefit of U.S. Provisional Patent Application No. 60/495,711, filedAug. 18, 2003, both of which are incorporated herein in their entiretyfor all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of balloon dilatation.Specifically, the present invention relates to balloons for dilatationapplications and a process for manufacturing the balloons.

2. Related Art

Surgical procedures employing balloons and medical devices incorporatingthose balloons (i.e. balloon catheters) are becoming more common androutine. These procedures, such as angioplasty procedures, are conductedwhen it becomes necessary to expand or open narrow or obstructedopenings in blood vessels and other passageways in the body to increasethe flow through the obstructed areas. For example, in the technique ofPercutaneous Transluminanl Coronary Angioplasty (PTCA), a dilatationballoon catheter is used to enlarge or open all occluded blood vesselwhich is partially restricted or obstructed due to the existence of ahardened stenosis or buildup within the vessel. This procedure requiresthat a balloon catheter be inserted into the patient's body andpositioned within the vessel so that the balloon, when inflated, willdilate the site of the obstruction or stenosis so that the obstructionor stenosis is minimized, thereby resulting in increased blood flowthrough the vessel. Often, however, a stenosis requires treatment withmultiple balloon inflations. Additionally, many times there are multiplestenoses within the same vessel or artery. Such conditions require thateither the same dilatation balloon must be subjected to repeatedinflations, or that multiple dilatation balloons must be used to treatan individual stenosis or the multiple stenoses within the same vesselor artery. Additionally, balloons and medical devices incorporatingthose balloons may also be used to administer drugs to patients.

Balloon catheters traditionally comprise a dilatation balloon at theirdistal end. Angioplasty balloons are currently produced by a combinationof extension and stretch blow molding. The extrusion process is used toproduce the balloon tubing, which essentially serves as a pre-form. Thistubing is subsequently transferred to a stretch blow-molding machinecapable of axially elongating the extruded tubing. U.S. Pat. No.6,328,710 B1 to Wang et al., discloses such a process, in which tubingpre-form is extruded and blown to form a balloon. U.S. Pat. No.6,210,364 B1; U.S. Pat. No. 6,283,939 B1 and U.S. Pat. No. 5,500,180,all to Anderson et al., disclose a process of blow-molding a balloon, inwhich a polymeric extrudate is simultaneously stretched in both radialand axial directions. Dilatation balloons arc subsequently attached to acatheter shaft and wrapped down tightly on this shaft in order toachieve a low profile at the distal end of the catheter. The low profileserves to enhance the ability of a dilatation catheter to navigatenarrow lesions.

The basic design of dilatation balloons has remained, essentially,unchanged since conception. The materials used in balloons fordilatation are primarily thermoplastics and thermoplastic elastomerssuch as polyesters and their block co-polymers, polyamides and theirblock co-polymers and polyurethane block co-polymers. U.S. Pat. No.5,290,306 to Trotta et al., discloses balloons made from polyesteretherand polyetheresteramide copolymers. U.S. Pat. No. 6,171,278 to Wang etal., discloses balloons made from polyether-polyamide copolymers. U.S.Pat. No. 6,210,364 B1; U.S. Pat. No. 6,283,939 B1 and U.S. Pat. No.5,500,180, all to Anderson et al., disclose balloons made frompolyurethane block copolymers.

Traditionally, the balloons available to physicians were classified aseither “compliant” or “noncompliant.” This classification is based uponthe operating characteristics of the individual balloon, which in turndepended upon the process used in forming the balloon, as well as thematerial used in the balloon forming process. Both types of balloonsprovide advantageous qualities, which were not available from the other.

A balloon that is classified as “noncompliant” is characterized by theBalloon's inability to grow or expand appreciably beyond its rated ornominal diameter. “Noncompliant” balloons are referred to as havingminimal distensibility. In balloons currently known in the art (e.g.,polyamide block copolymers), this minimal distensibility results fromthe strength and rigidity of the molecular chains which make up the basepolymer, as well as tile orientation and structure of those chainsresulting from the balloon formation process. The strength resultingfrom this highly oriented structure is so great that when the balloon issubjected to typical inflation or operating pressures (i.e., about 70psi to over 200 psi), it will not be stressed beyond the failure pointof the polymeric material.

A balloon, which is referred to as being “compliant”, is characterizedby the balloon's ability to grow or expand beyond its nominal or rateddiameter. In balloons previously known in the art (e.g., polyethylene,polyvinylchloride), the balloon's “compliant” nature or distensibilityresults from the chemical structure of the polymeric material used inthe formation of the balloon, as well as the balloon forming process.These polymeric materials have a relatively low yield point. Thus, theinflation pressures used in dilation procedures are typically above theyield point of the materials used to form distensible balloons. Adistensible or “compliant” balloon when inflated to normal operatingpressures, which are greater than the polymer material's yield point, issubjected to stress sufficient to permanently realign the individualmolecular chains of the polymeric material. The realignment of theindividual polymer chains permits the balloon to expand beyond itsnominal or rated diameter. However, since this realignment is permanent,the balloon will not follow its original stress-strain curve on thesubsequent inflation-deflation cycles. Therefore, the balloon, uponsubsequent inflations, will achieve diameters that are greater than thediameters that were originally obtained at any given pressure during thecourse of the balloon's initial inflation.

The yield point of a material is defined as the stress at which theindividual molecular chains move in relation to one another such thatwhen the pressure or stress is relieved there is permanent deformationof the structure. The modulus of a material, also known as the Young'smodulus, is the stress per unit strain. A material, which exhibits theability to follow the same stress-strain curve during the repeatedapplication and relief of stress, is defined as being elastic and ashalving a high degree of elastic stress response.

Despite the use of high strength engineering polymers, access to highlyoccluded vessels and lesions in small vessels is still limited.Dilatation balloons currently available do not have a proper balance ofcompeting properties. Balloons are needed that have low profile and archighly elastic, but also have high strengths and have high trackabilityto maneuver through tortuous vessels. While balloons made frompolyethylene terephthalate (PET) can halve lower profile than otherballoons, such as polyamide copolymer balloons, the PET balloon isstiff, has a higher modulus, and therefore has inferior trackability.While balloons made from polyamide copolymers have better trackabilitythan PET balloons due to their lower modulus, they have higher profilesthus limiting their application.

Furthermore, in attempting to produce low profile balloons by wrappingthe balloon, the wrapping process often serves to reduce the burststrength of the balloon. An additional disadvantage is that dilatationballoons are not highly elastic. The initial low profile is onlyapplicable to the first lesion that is dilated, as the balloon does notre-wrap tightly upon deflation. In the event that a patient has multiplelesions, a new catheter is used for each lesion thus adding to the costand time of the procedure.

New dilatation balloon materials are needed that halve the properbalance of these competing properties. Also, new processes are needed toproduce dilatation balloons with the balanced properties. Dilatationballoons are needed that have low profile, high hoop strength,high-elasticity, high elastic recovery and high trackability.

SUMMARY OF THE INVENTION

It has been found that utilizing multiblock copolymers in solution orsolutionless extrusion processes allows for the production of dilatationballoons with low profile, high hoop strength, high-elasticity, highelastic recovery and high trackability. The unique mechanical responseof the balloons is due to the macroscopically aligned microdomains inthe multiblock copolymers, formed during the extrusion and balloonforming process.

In an embodiment, therefore, the present invention relates to azero-fold dilatation balloon comprising a multiblock copolymer havingelasticity at nominal strains equal to or greater than about 30% 40%,50%, 60%, 70%, 80%, 90% or 100%, where nominal strain is [(balloon o.d.at nominal pressure−preform o.d.)/preform o.d.]×100, where o.d. is outerdiameter.

In another embodiment, the present invention relates to a zero-folddilatation balloon comprising a multiblock copolymer having highelasticity and elastic recovery from nominal strains equal to or greaterthan about 30% 40%, 50%, 60%, 70%, 80%, 90% or 10%.

In another embodiment, the present invention relates to a self-wrappingdilatation balloon comprising a multiblock copolymer having highelasticity and elastic recovery from nominal strains equal to or greaterthan about 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100%.

Dilatation balloons of the present invention can be used in a wide rangeof applications for angioplasty, stent delivery and other applications,including, but not limited to cardiovascular, neurovascular andperipheral applications.

Dilatation balloons of the present invention for use in cardiovascularapplications, for example, encompass a range of balloon sizes, includingbut not limited to balloons having outer diameter at nominal pressuresof about 0.5 mm to about 60 mm. One example is a 3 mm balloon. The term“3 mm balloon” is used herein to refer to dilatation balloons with anouter diameter at nominal pressures of about 3 mm. The 3 mm balloons ofthe present invention exemplify and illustrate the unique mechanicalresponse of the dilatation balloons of the present invention. Forexample, the 3 mm balloons have hoop strengths of at least 14,000p.s.i., elastic recovery from nominal strains greater than about 30% andhigh elasticities. The 3 mm balloon has a non-linear compliance curvehaving initial, secondary and final segments, the initial segment havinga radial growth higher than the secondary segment, and the secondarysegment having a radial growth higher than the final segment. The radialgrowth for the 3 mm balloon in mm/p.s.i. is about 0.39 for the initialsegment, 0.025 for the secondary segment, and 0.017 for the finalsegment.

In another embodiment, the present invention relates to a polymericextrudate for making a dilatation balloon comprising a multiblockcopolymer having tensile strength in the range of about 50 MPa to about450 MPa, strain at break in the range of about 50% to about 600% andelasticity at nominal strains of at least about 30%.

In another embodiment, the present invention relates to a polymericextrudate for making a dilatation balloon comprising a multiblockcopolymer having tensile strength in the range of about 50 MPa to about450 MPa, strain at break in the range of about 50% to about 600% andsubstantially complete elastic recovery from strains of at least about30%. One particular, non-limiting example is an extrudate for making a 3mm balloon having tensile strength in the range of about 150 MPa toabout 250 MPa, strain at break in the range of about 300% to about 500%and substantially complete elastic recovery from strains of at leastabout 30%. An alternative example is ail extrudate having tensilestrength in the range of about 50 MPa to about 150 MPa, strain at breakin the range of about 50% to about 300% and substantially completeelastic recovery from strains of at least about 30%. Another example isan extrudate having tensile strength in the range of about 250 MPa toabout 450 MPa, strain at break in the range of about 500% to about 600%and substantially complete elastic recovery from nominal strains of atleast about 30%.

Extrudates of the present invention can have a tubular shape. Extrudatescan have outer diameter of about 0.025 mm to about 13 mm and innerdiameter of about 0.013 mm to about 12 mm. In one particular example, anextrudate for a 3 mm balloon, can have a tubular shape with an outerdiameter of about 0.25 mm to about 2.5 mm and ail inner diameter ofabout 0.15 mm to about 1.5 mm. The extrudates of the present invention,including, but not limited to the extrudate for the 3 mm balloon, havephase-separated microdomains that are macroscopically aligned inparallel, perpendicular, transverse, or a combination thereof.Alternatively, the extrudate can have two or more regions with differentmacroscopic microdomain alignment.

In another embodiment, the present invention relates to a process forproducing a polymeric extrudate for use as a dilatation balloon. Theprocess comprises contacting a multiblock copolymer with a solvent toform a multiblock copolymer mixture, extruding the multiblock copolymermixture to form an extrudate, and drawing the extrudate, wherein theextrudate has tensile strength in the range of about 50 MP a to about450 MPa, strain at break in the range of about 50% to about 600% andelasticity at nominal strains of It least about 30%. Optionally, theextrudate has substantially complete elastic recovery from nominalstrains of at least about 30%.

In another embodiment, the present invention relates to an alternativeprocess for producing a polymeric extrudate for use as a dilatationballoon. The process comprises extruding a multiblock copolymercomposition to form an extrudate, and drawing the extrudate, wherein theextrudate has tensile strength in the range of about 50 MPa to about 450MPa, strain at break in the range of about 50% to about 600% andelasticity at nominal strains of at least about 30%.

In the process, the extruding is done at a constant rate such that theextrudate has phase-separated microdomains that are macroscopicallyaligned in parallel, perpendicular, transverse, or a combinationthereof. Alternatively, the extruding is done at a variable rate suchthat the extrudate has two or more regions with different microscopicmicrodomain alignment. The temperature of the extrusion is equal to orless than the order-disorder transition temperature for the multiblockcopolymer. After extrusion, the process optionally comprises the step ofcoagulating the extrudate.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by thestructure and particularly pointed out in the written description andclaims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are included to illustrate exemplaryembodiments of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 shows idealized (prophetic) compliance curves for the dilatationballoons of the present invention as compared to a standard 3.00 mmballoon.

FIG. 2 shows the idealized (prophetic) true stress vs. nominal straincurves for a cylindrical dilatation balloon of the present invention ascompared to a standard polyamide copolymer balloon, both duringinflation.

FIG. 3A illustrates a cross-sectional view of a traditional balloonwrapped around a catheter.

FIG. 3B illustrates a side-view of a traditional balloon wrapped arounda catheter.

FIG. 4A illustrates a cross-sectional view of a zero-fold balloonmounted on a catheter, according to an embodiment of the presentinvention.

FIG. 4B illustrates a side-view of a zero-fold balloon mounted on acatheter, according to an embodiment of the present invention.

FIG. 5A is a flow diagram for a process for producing a polymericextrudate for use as a dilatation balloon, according to an embodiment ofthe present invention.

FIG. 5B is a flow diagram for an alternative process for producing apolymeric extrudate for use as a dilatation balloon, according to anembodiment of the present invention.

FIGS. 6A-6B show stress vs. strain curves for a multiblock copolymerextruded according to an embodiment of the present invention.

FIG. 7A shows stress vs. strain curves for extruded multiblock copolymersamples before straining, according to an embodiment of the presentinvention.

FIG. 7B shows stress vs. strain curves for extruded multiblock copolymersamples after straining, according to an embodiment of the presentinvention.

The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements. Additionally, the left-mostdigit(s) of a reference number identifies the drawing in which thereference number first appears.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings.

Preform is used herein to refer to the drawn, uniaxially or biaxially,tubular extrudate formed upon extruding and drawing the multiblockcopolymer mixture or composition. The preform is used in the process ofproducing a dilatation balloon. The process of forming dilatationballoons from tubular preforms are well known to one of skill in therelevant art. The preform can be a drawn extrudate, formed upon drawingthe extrudate in, for example, a balloon forming machine. Extrudate isused herein to refer to the article formed by extruding the multiblockcopolymer mixture or composition. The extrudate can be used in forming adilatation balloon preform, or optionally, call be used in forminganother article, for example, a tubular extrudate for use in anothermedical application.

The terms “microdomain” and “microphase” are used generally to refer tothe domains and phases in the multiblock copolymers. The terms“microdomain” and “microphase” should not be construed to be limiting inthe size of the domain or phase. The terms “microdomain” and“microphase” are understood to include, but are not limited tonanometer-sized domains and phases such as nanodomains and nanophases,micrometer-sized domains and phases such as microdomains andmicrophases, and other sized domains and phases.

The term “dilatation balloon” refers generally to the types of balloonsincluded in the present invention. Dilatation balloon, for example,includes, but is not limited to angioplasty balloons, stent deliveryballoons and others. It should be understood that the term “dilatationballoon” is referred to throughout the description herein forillustrative purposes, and it is intended that the descriptions hereinencompass different balloon sizes depending on the application. Althoughspecific examples of balloons for particular applications are describedfor exemplary purposes, it should be understood that the scope of theinvention is not limited to the exemplified balloons. While the balloonsof the present invention can vary in size, and can be used for differentapplications, they all exhibit the unique mechanical response describedherein, namely, they exhibit low profile, high hoop strength,high-elasticity, high elastic recovery and high trackability.

One embodiment of the present invention relates to a zero-folddilatation balloon comprising a multiblock copolymer having high hoopstrength, high elasticity and high elastic recovery.

Another embodiment of the present invention relates to a self-wrappingdilatation balloon comprising a multiblock copolymer having high hoopstrength, high elasticity and high elastic recovery.

The balloons of the present invention are formed from multiblockcopolymers and exhibit high elasticity. For example, the 3 mm balloonexhibits high elasticity over an initial low-inflation pressure range.FIG. 1 shows an example of an idealized or prophetic compliance curvefor 3 mm balloons of the present invention compared to conventional 3 mmballoons. In zone 1 of FIG. 1, the high elasticity zone, 3 mm balloonsof the present invention have a growth rite of about 0.39 mm/p.s.i.,compared to about 0.08 mm/p.s.i. for the conventional balloons. Thehyper-elastic characteristics of the balloons of the present inventionallow for zero-fold and self-wrapping characteristics. Other sizedballoons of the present invention exhibit similar, highly elasticresponses.

FIG. 2 shows the corresponding true stress vs. nominal strain responsefor both 3 mm balloon inflations shown in FIG. 1. The idealized orprophetic response curve highlights, for 3 mm dilatation balloons of thepresent invention, the initial high elasticity zone and low modulus overthe initial high elasticity zone. A sharp transition cal be seen to theinelastic-high strength zone. Minimal hysteresis in the dilatationballoons of the present invention ensures complete elastic recovery tothe initial balloon form and dimensions. The stress-strain curve for theconventional polyamide copolymer balloon shows that materials used tomanufacture conventional balloons exhibit significantly less elasticity,over the initial elasticity zone, and modulus typically higher than the3 mm dilatation balloons of the present invention.

The term wrapping is well known to one of ordinary skill in the art andrefers to how the dilatation balloon is disposed about a catheter tocreate a low profile during delivery of the balloon to the treatmentsite. Traditionally, a dilatation balloon is wrapped down tightly on acatheter shaft, in a separate manufacturing process, to achieve a lowprofile at the distal end. FIG. 3A shows a cross section of atraditional balloon catheter assembly 300 having a balloon 302 wrappeddown tightly on a catheter shaft 304. FIG. 3B shows a side view ofwrapped balloon 302 and catheter shaft 304. The wrapping process,however, often reduces the burst strength of the balloon. In addition,the initial low profile of the wrapped balloon is only applicable beforeinitial inflation and to the first lesion that is dilated, because theballoon typically does not re-wrap as tightly upon deflation. The numberof lesions that can be treated with a traditional wrapped balloon islimited.

In contrast to the balloons of the prior art, the balloons of thepresent invention are zero-fold, have low profiles and have highelasticity. The phrase zero-fold is used herein to refer to balloonsthat preferably have no folds or wraps. Alternatively, balloons of thepresent invention have substantially no folds or wraps and have a lowerprofile than the balloons in the current art. For example, FIG. 4A showsa cross section of a zero-fold balloon catheter assembly 400 having aballoon 402 mounted on a catheter shaft 404. FIG. 4B shows at side viewof zero-fold balloon 402 mounted on catheter shaft 404. Zero foldballoons of the present invention have high elasticity and high elasticrecovery, which gives rise to self-wrapping characteristics.Self-wrapping refers to the characteristic of a highly elastic balloonwhere, after initial inflation and upon deflation, the balloon returnsto a low profile over the catheter tubing. Preferably, the balloonreturns to approximately the same low profile it had before the initialinflation.

In fact, before initial inflation and when deflated, the zero-foldballoons of the present invention have a much lower profile than wrappedconventional balloons, and can have essentially the same dimensions asthe tubular pre-form. When inflated, balloons of the present inventiontransition from a low profile tube to a conventional balloon and revertto the initial tubular form when deflated, even after multipleinflations and after multiple lesions have been dilated. Balloons of thepresent invention have elasticity at nominal strains of at least about30%. Alternatively, balloons of the present invention have elasticrecovery from nominal strains equal to or greater than about 30%, 40%,50%, 60%, 70%, 80%, 90% or 100%, where nominal strain is [(balloon o.d.at nominal pressure−preform o.d.)/preform o.d.]×100, where o.d. is outerdiameter. The balloons of the present invention may, therefore, be usedto dilate multiple lesions without compromising primary performance.

The low profile of the present invention allows a surgeon to use theballoon in very small arteries that may have a large degree of blockageor plaque build-up. Conventional 3.0 mm balloons at zero atmosphereshave an outer diameter of about 2.5 mm when deflated and inflate toabout 3.0 to about 3.3 mm when close to bursting. Balloons of thepresent invention can have much lower profile and maintain high hoopstrength, allowing for their use in a wider range of applications. Forexample, 3 mm dilatation balloons of the present invention can haveouter diameters of about 0.25 mm to about 2.5 mill when deflated andabout 3.5 mm to about 4.0 mm outer diameter when inflated close tobursting. Alternatively, the balloons of the present invention can beproduced to have lower profiles for other applications, for example,neurovascular applications. Alternatively, the balloons can be producedto have lower or larger profiles for other applications, for exampleperipheral applications.

Dilatation or distensibility is used herein to refer to theexpandability of the balloon. Balloons of the present invention aresufficiently expandable to treat various sized arteries and for stentdelivery, i.e., have radial growths about 2% to about 40% betweennominal and rated pressures. Preferably, the radial growth of theballoon is in the range of about 5% to about 20%.

Balloons of the present invention have sufficient hoop strengths todilate occluded vessels without bursting and for stent delivery or otherapplications. Hoop strength is directly related to the maximum amount ofpressure the balloon call withstand, for a given material and a givenballoon wall thickness, without failing. The balloons of the presentinvention have hoop strengths upon dilatation of about 12,000 to about75,000 p.s.i. Preferably, balloons of the present invention have hoopstrengths greater than 14,000 p.s.i.

The unique mechanical response of the dilatation balloons of the presentinvention is achieved by utilizing multiblock copolymers in either asolutionless or solution extrusion process. The multiblock copolymer isextruded to form a polymeric extrudate that is a tubular pre-form. Theextrudate can be further processed using methods well known to one ofordinary skill in the art to produce the dilatation balloons of thepresent invention. Once formed, the balloons can be attached to thedistal end of a tubular elongated catheter shaft to form a balloondilatation catheter. The distal portion of the catheter cal have aprofile in the range of about 0.025 mm to about 13.0 mm when the balloonis deflated. For a 3 mm balloon, the distal portion of the catheter canhave a profile in the range of about 0.25 mm to about 2.5 mm when theballoon is deflated. The distal portion of the catheter can havesubstantially tile same profile after one or more expansions of theballoon with rated pressures that result in about 5% to about 20% radialgrowth of the balloon.

In another embodiment, the present invention relates to a polymericextrudate for making a dilatation balloon comprising a multiblockcopolymer. Multiblock copolymers, the corresponding polymeric extrudatesand dilatation balloons for use in the invention have a Young's Modulusless; than about 5 GPa.

Extrudates of the present invention have tensile strength in the rangeof about 50 MPa to about 450 MPa, strain at break in the range of about50% to about 600% and elasticity at nominal strains of at least about30%. Optionally, extrudates of the present invention also havesubstantially complete elastic recovery from nominal strains of at leastabout 30%. One particular, non-limiting example is all extrudate formaking a 3 mm balloon having tensile strength in the range of about 150MPa to about 250 MPa, strain at break in the range of about 300% toabout 500% and substantially complete elastic recovery from strains ofat least about 30%. An alternative example is all extrudate havingtensile strength in the range of about 50 MPa to about 150 MPa, strainat break in the range of about 50% to about 300% and substantiallycomplete elastic recovery from strains of at least about 30%. Anotherexample is an extrudate having tensile strength in the range of about250 MPa to about 450 MPa, strain at break in the range of about 500% toabout 600% and substantially complete elastic recovery from strains ofat least about 30%.

Multiblock copolymers for use in the present invention include thosemultiblock copolymers that microphase separate. Microphase separation isa phenomenon unique to copolymers and is well known in the art. See,e.g., Bates, F. S. and Fredrickson, G. H., Physics Today February, 1999,pages 32-38. Microphase separation occurs due to tile incompatibility ofthe polymeric blocks within the multiblock copolymer. Multiblockcopolymers can phase separate to form spherical, cylindrical, lamellaeor other structures of one block or phase, dispersed in a differentblock or phase. Using techniques well known in the art, for example,reciprocal shearing, the incompatible phases can be induced to orientmacroscopically, thereby inducing long-range order in separate phases.Macroscopic ordering or alignment of the separated blocks or phases canresult in a variety of alignments between the phases or microdomains.The size of the microdomains call vary from about 5 nm to about 1000 nm.These alignments include, but are not limited to parallel, perpendicularand transverse alignments. The different alignments give rise to highlyanisotropic mechanical responses for the resulting material. Therefore,dilatation balloons can be flexible and steerable, while having highhoop strength, high elasticity and high elastic recovery.

Any method known to one of skill in the relevant art can be used tomeasure the macroscopic ordering of the polymer blocks or phases, forexample, X-ray crystallography or diffractometry can be used. UsingX-ray diffractometry, both the type of alignment and the degree ofalignment can be measured in tile extrudates and the dilatation balloonsof the present invention.

Examples of multiblock copolymers for use in the present inventioninclude, but are not limited to diblock, triblock, butablock,pentablock, hexablock, heptablock, octablock, nonablock, decablock,undecablock or dodecablock copolymers. The choice of number of blocksdepends on the microphase separation and mechanical response needed. Asthe number of blocks is increased, the level of microphase separationand the macroscopic alignment decreases with detrimental effects to themechanical response of the dilatation balloon.

Multiblock copolymers can have two different polymer blocks, oralternatively, they can have three or more different polymer blocks. Forexample, a triblock copolymer can have two different polymer blocks,represented as (A-B-A), or alternatively, it can halve three differentpolymer blocks, represented as (A-B-C). A single multiblock copolymercan be used, or alternatively, a combination or blend of two or more ofthe same or different multiblock copolymers can be used. For example, adilatation balloon of the present invention can comprise 100% triblockcopolymer plus other optional additives, or alternatively, it cancomprise 10% pentablock copolymer and 90% triblock copolymer plus otheroptional additives.

The polymer blocks can have any chemical structure, so long as themultiblock copolymer microphase separates. Examples of polymer blocksfor use in the invention include, but are not limited to polyalkanesoptionally substituted by alkyl, halo, ester, aryl and heteroaryl,polyhaloalkanes, polyalkenes, polyalkynes, polyarylenes, polyethers,polythioethers, polyesters, polycarbonates, polyamides, polyimides,polyurethanes, polyureas, polysulfones, polyketones, polysaccharides,polyamines, polyimines, polyphosphates, polyphosphonates,polysulfonates, polysulfonamides, polyphosphazenes and polysiloxanes.Specific examples include, but are not limited to polyethylene,polypropylene, poly(cylohexylethylene), polyisoprene,poly(1,3-butadiene), poly(vinyl chloride), poly(vinyl fluoride),poly(chloroprene), poly(methyl acrylate), poly(methyl methacrylate),poly(acyrlonitrile), polystyrene or poly(4-vinylpyridine). The polymerblocks can be of any molecular weight, as long as the resultingmultiblock copolymer microphase separates. The length of each polymerblock affects the orientation of the microphase separation. For example,polymer blocks can range from a single repeat unit to about one millionrepeat units. More specifically, polymer blocks can have molecularweights of about 10 Dalton to about 10,000,000 Dalton.

Specific examples of block copolymers for use in the present inventioninclude but are not limited to triblock and pentablock copolymers havingABA and ABABA architectures, respectively, wherein A is a glassy phaseand B is a random copolymer comprising rubber and semi-crystallinephases. Specific examples of polymers include, but are not limited topoly(vinylcyclohexane) or hydrogenated poly(styrene) for the glassyphase; hydrogenated 1,2 poly(butadiene) for the rubber phase; andhydrogenated 1,4 poly(butadiene) for the semi-crystalline phase. Thephysical properties of the extrudate and/or the dilatation balloon canbe enhanced by tailoring one or more phases of the block copolymer. Aspecific example of this tailoring includes, but is not limited toincreasing the linearity of the semi-crystalline phase to increase itscrystallinity and thereby increase the strength of the extrudate and/ordilatation balloon.

Extrudates comprising multiblock copolymers for use in producingballoons of the present invention comprise a single layer of polymericmaterial. Alternatively, two or more layers of polymeric extrudate andmultiblock copolymers can be used to form multilayered extrudates andmultilayered dilatation balloons.

The polymeric extrudate optionally comprises a solvent. Any solvent orfluid can be used. The solubility parameter of the solvent is preferablyabout equal to the solubility parameter of one polymer block in themultiblock copolymer. The solubility parameter is a numerical value thatindicates the relative solvency behavior of a specific solvent.Solubility parameters for many solvents are well known in the art. Thesolvent is selected so that it reduces entanglement in one of thepolymer block phases, preferably the most entangled phase. For example,dioctylphthalate is used in reducing the entanglement in a polyethylenephase of triblock co-polyethylene co-poly(cyclohexylethylene).

Optionally, the solvent comprises a plasticizer. Alternatively, thesolvent is a plasticizer. Plasticizer is used herein to mean anymaterial that can decrease the flexural modulus of a polymer.Preferably, the solubility parameter of the plasticizer is about equalto the solubility parameter of one polymer block in the multiblockcopolymer. The plasticizer may influence the morphology of themultiblock copolymer and may affect the melting temperature, glasstransition temperature and order-disorder transition temperature.Examples of plasticizers include, but are not limited to: small organicand inorganic molecules, oligomers and small molecular weight polymers(those having molecular weight less than about 50,000), highly-branchedpolymers and dendrimers. Specific examples include: monomericcarbonamides and sulfonamides, phenolic compounds, cyclic ketones,mixtures of phenols and esters, sulfonated esters or amides,N-alkylolarylsulfonamides, selected aliphatic diols, phosphite esters ofalcohols, phthalate esters such as diethyl phthalate, dihexyl phthalate,dioctyl phthalate, didecyl phthalate, di(2-ethylhexy) phthalate anddiisononyl phthalate; alcohols such as glycerol, ethylene glycol,diethylene glycol, triethylene glycol, oligomers of ethylene glycol;2-ethylhexanol, isononyl alcohol and isodecyl alcohol, sorbitol andmannitol; ethers such as oligomers of polyethylene glycol, includingPEG-500, PEG-1000 and PEG-2000; and amines such as triethanol amine.

The extrudate optionally further comprises all additive or modifier.Additive and modifier are used herein to refer to any material added tothe polymer to affect the polymer's properties. Examples of additivesand modifiers for use in the invention include fillers, antioxidants,colorants, crosslinking agents, impact strength modifiers, viscositymodifiers, drugs and biologically active compounds and molecules.Specific examples include, but are not limited to the following. Across-linking agent, such as diallyl phthalate, can be used to increasethe mechanical strength of the extrudate and the resulting dilatationballoon. In another example, the additive comprises a polymer. Forexample, a multiblock copolymer mixture or composition comprising apentablock copolymer cal optionally further comprise a triblockcopolymer to facilitate processing and modify tile viscosity. In anotherexample, a multiblock copolymer mixture or composition can comprise ahomopolymer such as a polyethylene or a polysiloxane to facilitateprocessing and modify the viscosity. Polysiloxanes for use in thepresent invention as additives or modifiers can include anypolysiloxane, for example, a polydialkylsiloxane or polydiarylsiloxane,including but not limited to polydimethylsiloxane, polydiethylsiloxane,and polydiphenylsiloxane.

Extrudates of the present invention call have a tubular shape. Tubularis used herein to mean a hollow, cylindrical-shaped article having aninner diameter, all inner circumference, an outer diameter and all outercircumference with a wall thickness between tile outer and innercircumferences. Extrudates can have outer diameter of about 0.025 mm toabout 13 mm and inner diameter of about 0.013 mm to about 12 mm. Oneparticular example, an extrudate for a 3 mm balloon, cal have a tubularshape with outer diameter of about 0.25 mm to about 2.5 mm and an innerdiameter of about 0.15 mm to about 1.5 mm. The extrudates of the presentinvention, including, but not limited to the extrudate for the 3 mmballoon, have phase-separated microdomains that are macroscopicallyaligned in parallel, perpendicular, transverse, or a combinationthereof. Alternatively, the extrudate call have two or more regions withdifferent macroscopic microdomain alignment.

Extruders for use in the present invention include any extruder capableof forming tubular-shaped articles. Examples of extruders include, butare not limited to, single screw and double screw. Tile processingtemperature depends on the actual multiblock copolymer system beingused. Preferably, the temperature of extrusion is near theorder-disorder transition temperature for the multiblock copolymer orthe multiblock copolymer with optional solvent, additives or modifiers.

In another embodiment, the present invention relates to a process forproducing a polymeric extrudate for use as a dilatation balloon. In oneexample, FIG. 5A shows a flowchart 500 showing steps for producing apolymeric extrudate for use as a dilatation balloon. Flowchart 500begins with step 502. In step 502, a multiblock copolymer is contactedwith a solvent to form a multiblock copolymer mixture. As discussedabove, the solvent can comprise a plasticizer, or alternatively, is aplasticizer. The solvent is chosen such that it reduces the entanglementof one of the phases of the multiblock copolymer. Any solvent can beused. Preferably, the solvent or plasticizer has a solubility parameterabout equal to the solubility parameter of at least one of the polymerblock phases. Any concentration of solvent can be used. Preferably, theconcentration of solvent results in microphase separation andmacroscopic ordering and alignment of the microdomains during extrusion.The resulting mixture can optionally comprise additional additives andmodifiers.

Referring again to FIG. 5A, in step 504, the multiblock copolymermixture is extruded to form an extrudate. The temperature of theextrusion process is set near the order-disorder transition temperatureof the multiblock copolymer mixture, preferably just below it. The shearrate also affects the final macroscopic ordering and alignment of themicrodomains. The multiblock copolymer mixture can be extruded at aconstant shear rate such that the extrudate has microdomains that aremacroscopically aligned parallel, perpendicular. transverse, or acombination thereof. Alternatively, the mixture is extruded at avariable rate such that the extrudate has two or more portions withdifferent macroscopic microdomain alignment. For example, the shear ratecan be set such that the molecules are aligned perpendicular to theflow, either radially outward in a starburst pattern, or in cylinders.The extrudate can optionally be cooled as it exits the extruder. Anymethod of cooling can be used, preferably, some fluid, for example,water, is used to cool the extrudate.

Referring again to FIG. 5A, in step 506, the extrudate is drawn. Theextrudate can be drawn after exiting the extruder. Any method known toone of ordinary skill in the art can be used to draw the extrudate.Preferably, the extrudate is drawn during balloon forming. Preferably, astretch blow-molding or a balloon forming machine is used. The extrudatecan be drawn in any one direction, or in any combination of directions,for example, uniaxially or biaxially. Biaxial drawing can be performedin the longitudinal direction and the radial direction. The extrudatecan be drawn to ally draw ratio, including any uniaxial or any biaxialdraw ratio. In biaxial drawing, the radial and longitudinal draw ratioscan vary separately. The draw ratio affects tile final properties of theballoon. By way of example, for approximately a 3 mm balloon, theextrudate is drawn to about 200% to 700% in the radial direction.

Referring back to FIG. 5A, in step 508, the drawn extrudate iscoagulated. The extrudate is coagulated after drawing to remove solventfrom the drawn extrudate. Any method known to one skilled in therelevant art can be used to coagulate tile drawn extrudate. For example,a vacuum oven is used to remove the solvent. Alternatively, the drawnextrudate is coagulated in a suitable fluid. Suitable fluids includethose fluids that remove the solvent from the extrudate withoutdissolving the extrudate, for example a C₁-C₆, alcohol.

In another example, FIG. 5B shows flowchart 550 showing an alternativeprocess for producing a polymeric extrudate for use as a dilatationballoon. In this example, a solventless process is used in producing theextrudate. Flowchart 550 begins with step 552. In step 552, a multiblockcopolymer composition is extruded to form an extrudate. The multiblockcopolymer composition comprises a multiblock copolymer. The multiblockcopolymer composition can optionally further comprise other additives,modifiers or a plasticizer. As above, the temperature of extrusion ispreferably set near the order-disorder transition of the composition.Also, as above, the shear rate can be constant or varied, depending onthe desired final orientation of the molecules in the extrudate. Also,as above, the extrudate can be cooled as it exits the extruder.Flowchart 550 continues with step 506. In step 506, the extrudate isdrawn.

An extrudate is formed having tensile strength in the range of about 50MPa to about 450 MPa, strain at break in the range of about 50% to about600% and elasticity at nominal strains of at least about 30%.Optionally, extrudates have substantially complete elastic recovery fromnominal strains of at least about 30%. One particular, non-limitingexample is a multiblock copolymer mixture is extruded to form anextrudate for making a 3 mm balloon having tensile strength in the rangeof about 150 MPa to about 250 MPa, strain at break in the range of about300% to about 500% and substantially complete elastic recovery fromstrains of at least about 30%. An alternative example is all extrudatehaving tensile strength in the range of about 50 MPa to about 150 MPa,strain at break in the range of about 50% to about 300% andsubstantially complete elastic recovery from strains of at least about30%. Another example is an extrudate having tensile strength in therange of about 250 MPa to about 450 MPa, strain at break in the range ofabout 500% to about 600% and substantially complete elastic recoveryfrom strains of at least about 30%.

The following examples are illustrative, but not limiting, of the methodand compositions of the present invention. Other suitable modificationsand adaptations of the variety of conditions and parameters normallyencountered in nanocrystal synthesis and which are obvious to thoseskilled in the art are within the spirit and scope of the invention.

EXAMPLE 1

A polymeric extrudate was formed as a tubular preform for a dilatationballoon. A multiblock copolymer was used as the base material. Atriblock copolymer was used having the structure (C-E-C), wherein C andE denote poly(cyclohexylethylene) (PCHE) and hydrogenated butadiene,respectively. The butadiene block is a mixture of 1-2 and 1-4 addition,which upon hydrogenation, results in a block of random poly(ethylene)(PE) and poly(ethylethylene) (PEE). The triblock copolymer is describedin detail in U.S. Pat. No. 6,455,656 B2; U.S. Pat. No. 6,451,924 B1;U.S. Pat. No. 6,426,390 B1; and U.S. Pat. No. 6,376,621 B1, all of whichare incorporated herein in their entireties by reference. The triblockpolymer was dissolved in dioctylphthalate (DOP), where the polymerconcentration was about 75 wt. %, thus creating a gel. The gel wasextruded at a temperature just below the order-disorder transitiontemperature. The gel was subsequently drawn to 400%. The extruded anddrawn samples were coagulated in a vacuum oven to extract the solvent.For Deborah numbers between 1 and 100, the macroscopic microdomainalignment was perpendicular as shown by Small Angle X-ray Scattering(SAXS) experiments and Transmission Electron Microscopy (TEM). As theDeborah number is proportional to shear rate, increasing the shear rateincreases the amount of perpendicular alignment. The size of themicrodomains measured about 10-20 nm. The extrudate was found to havehoop strength in excess of 150 MPa, strain at break of 120%, andcomplete elastic recovery after subjecting the extrudate to strains ashigh as 40%.

EXAMPLE 2

Following a similar procedure, a pentablock copolymer was extrudedhaving structure (C-E-C-E-C), wherein C and E denotepoly(cyclohexylethylene) (PCHE) and hydrogenated butadiene,respectively. The butadiene block is a mixture of 1-2 and 1-4 addition,which upon hydrogenation, results in a block of random poly(ethylene)(PE) and poly(ethylethylene) (PEE). The polymer is described in U.S.Pat. No. 6,455,656 B2; U.S. Pat. No. 6,451,924 B1; U.S. Pat. No.6,426,390 B1; and U.S. Pat. No. 6,376,621 B1. For Deborah numbersbetween 0.1 and 100, the macroscopic microdomain alignment wasperpendicular, and a transverse alignment was also seen for Deborahnumbers between 10 and 100. Similar mechanical responses were measuredfor the pentablock copolymer as the triblock copolymer, except thepentablock copolymer was found to have superior strength-elasticitybalance as compared with the triblock extrudate.

Following a similar procedure, one can produce tubular preformscomprising a blend of 90% of the (C-E-C) triblock copolymer and 10% ofthe (C-E-C-E-C) pentablock copolymer.

One can attach the extrudates formed above to a catheter to form a lowprofile, self-wrapping dilatation catheter balloon for angioplastyapplications.

EXAMPLE 3

Following a similar procedure as Example 1, a pentablock copolymerhaving molecular weight of about 65 kg/mole and comprising about 60 wt.% of the poly(cyclohexylethylene) block and about 10 wt. % of thepoly(ethylethylene) block was mixed with dioctylphthalate to form a gelhaving about 75 wt. % polymer. The gel was extruded and the extrudatewas pre-strained or aligned by hand. The elasticity and elastic recoveryof the sample was studied using a tensile machine. FIGS. 6A and 6B showthe stress vs. strain (hysteresis) curves. The curves show that thematerial is highly elastic and substantially recovers from strains ofabout 4, 10, 18 and 40% without permanent deformation. FIG. 6A shows nofailure of the material until strains of about 120%.

EXAMPLE 4

A series of samples were extruded comprising a pentablock copolymer andvarying amounts of solvent. The pentablock copolymer had molecularweight of about 55 kg/mol and comprised about 55 wt. %poly(cyclohexylethylene) and about 10 wt. % poly(ethylethylene).Dioctylphthalate was mixed with the pentablock copolymer to form 6samples, having 100, 95, 90, 85, 80 and 75 wt. % polymer. The sampleswere extruded with a capillary rheometer. The temperature of thecapillary wais set at about 125° C. The capillary die was about 1 mm indiameter and about 30 mm in length. A shear rate of about 11.5 s⁻¹ wasused in the extrusion. After extrusion, the extrudate was pre-strainedby hand and post-strained using all tensile machine to the completion ofnecking. The mechanical properties of the samples were then analyzedusing a tensile machine. FIG. 7A shows stress-strain curves for the sixsamples before straining and FIG. 7B shows stress-strain curves for thesix samples after straining. The results show that the 75 wt. % gelsample had the greatest elastic response compared to the other samples.

It will be understood by those skilled in the art that various changesin form and details may be made therein without departing from thespirit and scope of the present invention as defined in the appendedclaims. Thus, the breadth and scope of the present invention should notbe limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1-25. (canceled)
 26. A process for producing a dilatation balloon, theprocess comprising: providing a multiblock copolymer compositioncomprising a multiblock Copolymer, wherein the multiblock copolymercomprises glassy phase end blocks, and blocks adjacent to the end blockscomprising rubber and semi-crystalline phases; and forming a dilationballoon comprising extruding the multiblock copolymer composition toform an extrudate comprising phase-separated glassy, rubber, andsemi-crystalline microdomains that are macroscopically ordered in aperpendicular alignment; wherein the dilatation balloon demonstrates,during inflation, a true stress vs. nominal strain response curvecomprising a first zone representative of a low modulus balloon, asecond zone representative of a high strength balloon, and a sharptransition from the first zone to the second zone.
 27. (canceled) 28.The process of claim 26, wherein said multiblock copolymer is apentablock copolymer, a heptablock copolymer, or a nonablock copolymer.29. The process of claim 26, wherein at least one block of saidmultiblock copolymer is polyethylene, polypropylene,poly(cylohexylethylene), polyisoprene, poly(1,3-butadiene), poly(vinylchloride), poly(vinyl fluoride), poly(chloroprene), poly(methylacrylate), poly(methyl methacrylate), poly(acrylonitrile), polystyreneor poly(4-vinylpyridine).
 30. The process of claim 28, wherein saidmultiblock copolymer is a pentablock copolymer comprisingpoly(cyclohexylethylene) and polyethylene blocks.
 31. The process ofclaim 26, wherein said multiblock copolymer composition furthercomprises an additive.
 32. The process of claim 31, wherein saidadditive is a homopolymer.
 33. The process of claim 32, wherein saidhomopolymer is a polydialkylsiloxane or polyethylene. 34-38. (canceled)39. The process of claim 31, wherein said additive comprises at leastone of a filler, antioxidant, colorant, crosslinking agent, impactstrength modifier, drug or biologically active material.
 40. The processof claim 26, wherein said multiblock copolymer composition furthercomprises a plasticizer.
 41. The process of claim 40, wherein saidplasticizer is a carbonamide, sulfonamide, phenolic compound, cyclicketone, mixture of phenols and esters, sulfonated ester, sulfonatedamide, N-alkylolarylsulfonamide, phthalate ester, amine, aliphatic diolor phosphite ester of an alcohol.
 42. The process of claim 26, whereinsaid multiblock copolymer composition further comprises a solvent. 43.The process of claim 42 further including coagulating the extrudate toremove solvent.
 44. The process of claim 42, wherein the solubilityparameter of said solvent and at least one block of said multiblockcopolymer are about equal.
 45. The process of claim 26, wherein saidextruding comprises extruding at a constant shear rate.
 46. The processof claim 26, wherein said dilatation balloon formed is a zero-foldballoon.
 47. The process of claim 46, wherein said zero-fold dilatationballoon is self-wrapping.
 48. The process of claim 26, wherein saidmultiblock copolymer composition is a blend of two or more multiblockcopolymers.
 49. The process of claim 26, wherein forming a dilationballoon further comprises drawing said extrudate.
 50. The process ofclaim 26, wherein forming a dilation balloon further comprises stretchblow-molding said extrudate.
 51. A process for producing a dilatationballoon, the process comprising: providing a multiblock copolymercomposition comprising a pentablock copolymer, wherein the multiblockcopolymer is a pentablock copolymer, a heptablock copolymer, or anonablock copolymer, and wherein the multiblock copolymer comprisesglassy phase end blocks, and blocks adjacent to the end blockscomprising rubber and semi-crystalline phases; and forming a dilatationballoon comprising extruding the multiblock copolymer composition at aconstant shear rate to form an extrudate comprising phase-separatedglassy, rubber, and semi-crystalline microdomains that aremacroscopically ordered in a perpendicular alignment; wherein thedilatation balloon, during inflation, demonstrates a true stress vs.nominal strain response curve comprising a first zone representative ofa low modulus balloon, a second zone representative of a high strengthballoon, and a sharp transition from the first zone to the second zone.52. The process of claim 51, wherein forming a dilation balloon furthercomprises drawing said extrudate.
 53. The process of claim 51, whereinforming a dilation balloon further comprises stretch blow-molding saidextrudate.
 54. A process for producing a dilatation balloon, the processcomprising: providing a multiblock copolymer composition comprising apentablock copolymer, wherein the pentablock copolymer comprises glassyphase end blocks, and blocks adjacent to the end blocks comprisingrubber and semi-crystalline phases; and forming a dilatation ballooncomprising: extruding the multiblock copolymer composition at a constantshear rate to form an extrudate comprising phase-separated glassy,rubber, and semi-crystalline microdomains that are macroscopicallyordered in a perpendicular alignment; and drawing said extrudate,wherein the dilatation balloon, during inflation, demonstrates a truestress vs. nominal strain response curve comprising a first zonerepresentative of a low modulus balloon, a second zone representative ofa high strength balloon, and a sharp transition from the first zone tothe second zone.